growth and ageing Flashcards
growth can involve 2 cellular changes, what are these?
- increase in cell numbers (hyperplasia)
- increase in cell size (hypertrophy)
which cells cannot regenerate?
neurons
growth can be affected by which 2 factors?
- genetic
- environmental
humans have 2 main growth phases, when are these?
- birth
- around 12
name hormones that influence growth
- thyroid hormone
- growth hormones
- sex hormones
- insulin
- cortisol
- parathyroid hormone
thyroid hormone is essential for normal growth and development, what role does it play?
- essential fro protein synthesis in foetal/infant brain
- required for normal development of neurons
- necessary for childhood growth
- facilitate action of growth hormone and sympathetic nervous system
what effect might hypothyroidism have on a growing child?
- impede brain and skeletal growth
- delayed tooth eruption
- growth defects
what re the metabolic actions of growth hormone?
- increase blood glucose
- decrease glucose uptake by cells
- increased lipolysis (make fatty acids available)
- facilitate uptake of amino acids for proteins synthesis
- cartilage/bone/soft tissue/viscera growth
describe hypothyroid dwarfism
- missing thyroid hormone
- infant proportions
describe hypopituitary dwarfism
- missing growth hormone
- normal proportions
which 2 hormones are responsible for the pubertal growth spurt?
oestrogen and testosterone
the effects of oestrogen and testosterone are mediated by an increase in which 2 hormones?
GH and IGF-1
what effects do oestrogen and progesterone have on bone growth?
- stimulate bone growth
- accelerate closure of epiphyseal growth plates
describe the anabolic effect of testosterone
-effect on protein synthesis increasing muscle bulk
insulin has no direct effect on growth, how does it contribute indirectly?
- promote foetal growth
- promote post-natal growth by stimulating IGF-1
- facilitate protein synthesis
cortisol, when present in high levels, has what effect on growth?
inhibits it
what effects does cortisol have on growth?
- stimulate protein catabolism
- suppress bone growth and promotes resorption
what role do Vii D and parathyroid hormone play in growth?
- ensure adequate amounts of calcium and phosphate areavaailable for bone formation
- Vit D absorbs calcium from gut
- PTH raises plasma calcium levels
what effect does excess growth hormone have on children?
accelerates growth - gigantism
what effect does excess growth hormone have on adults?
acromegaly
which bone enlargens due to pituitary tumour?
sella turcica
what is the name for defective cartilage growth?
achondroplasia
what is the definition for ageing?
gradual deterioration of all parts of the body
what happens to cells during ageing?
- decline in the ability of them to divide
- as they divide there is an accumulation of damage (error in DNA, abnormal proteins, damaged organelles)
- free radicals
